Employee Retirement Benefits - The liability and expense reflected in the balance sheet and income statement (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Long-term portion in other liabilities	$ 7,998	$ 8,072	$ 7,348
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning liability balance	8,307	7,560	5,969
Net periodic benefit cost	733	755	582
Other comprehensive (income) loss	(523)	200	1,236
Total recognized in net and other comprehensive income	210	955	1,818
Retiree benefits paid	(263)	(208)	(227)
Ending liability balance	8,254	8,307	7,560
Current portion in accrued liabilities	255	235	212
Long-term portion in other liabilities	7,999	8,072	7,348
Assumptions used to calculate benefit obligation:
Discount rate	4.50%	4.25%	4.50%
Wage inflation rate	4.00%	4.00%	4.00%
Assumed health care cost trend rate	7.70%	8.10%	8.60%
Ultimate health care cost trend rate	5.00%	5.00%	5.00%
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates
Effect on total of service and interest cost components, one percentage point increase	145
Effect on total of service and interest cost components, one percentage point decrease	(107)
Effect on accumulated postretirement benefit obligation, one percenatge point increase	1,542
Effect on accumulated postretirement benefit obligation, one percenatge point decrease	$ (1,198)